Inorganic peroxide is usually defined as hydrogen peroxide and adducts thereof. Some examples are: hydrogen peroxide, carbamide peroxide, sodium percarbonate, sodium perborate. Peroxide is used in many different applications from an antiseptic for minor wounds to bleach for teeth, hair and laundry. Solutions of varying strengths of hydrogen peroxide are readily on the market, usually in a liquid form.
For targeted bleaching applications, such as tooth whitening, it can be desirable to blend the peroxide into a gel by blending the peroxide with a thickener. Blending is accomplished by mixing the thickener with the peroxide, usually also with water or an appropriate organic solvent. However, due to the volatile oxidizing nature of peroxide (which imparts the substance's bleaching ability); there are very few thickeners that can withstand a peroxide environment. Most polymers will degrade quickly in a peroxide environment and will lose their thickening properties entirely due to the powerful oxidizing effects of peroxide. These gels will degrade into thin, water-type consistencies. It is rare to find a polymer that can withstand, for prolonged periods of time, the powerful effects of peroxide.
Chemists have diluted hydrogen peroxide in order to tame its instability and raw oxidizing power. Liquid hydrogen peroxide is common and is by far the most aggressive oxidizer and the most unstable. Chemists have also produced adducts of hydrogen peroxide to stabilize hydrogen peroxide in the resultant compounds. The main adducts of hydrogen peroxide that are used for bleaching are: urea hydrogen peroxide (carbamide peroxide), sodium perborate, and sodium percarbonate. However, dilution of hydrogen peroxide by any means, while increasing stability, also reduces the bleaching efficacy of resultant gels. Carbamide peroxide contains about 36% hydrogen peroxide by weight. Therefore, a bleaching gel made with about 10% carbamide peroxide (which is an industry standard), yields only about 3% hydrogen peroxide. Sodium percarbonate has an even lower concentration of hydrogen peroxide. The use of these adducts then, generates an instant upper limit to the final concentration of hydrogen peroxide in a product.
Dental whitening manufacturers have predominately been using carbamide peroxide. Carbamide peroxide is docile enough to be used with many polymers that would not work with hydrogen peroxide. The most used commercial thickener, CARBOPOL, is a good example of this. CARBOPOL is a good thickener for carbamide peroxide. However, CARBOPOL does not hold up to pure hydrogen peroxide for even short amounts of time. When CARBOPOL is used in a composition containing 30% hydrogen peroxide, the composition will begin to break down and form peroxide decomposition bubbles in about two weeks. Therefore what is needed is a polymer that is capable of withstanding hydrogen peroxide compositions for moderate amounts of time.
The direct application of these manufactured gels and liquids to the teeth for the purpose of bleaching does have drawbacks. Direct delivery of these gels and liquids onto the teeth can be unsuccessful as they tend to run-off the teeth by the force of gravity. They also are subject to being wiped off quickly by the cheeks and gums. To make matters worse, the saliva is also there to quickly wash and dilute any treatment fluids off of the teeth. While gels may be more resistant to these drawbacks as compared to other liquids, they still have these inherent difficulties.
In order to overcome the difficulties inherent in the direct application of fluidic treatment materials various inventions have been developed. One of the early inventions involved an insoluble barrier that would hold the treatment gels and liquids against the teeth and at the same time protect it against the tongue, cheek and saliva. This resulted in the invention of the plastic dental tray. The major drawback in the concept of a tray is that the variations in teeth anatomy make it very difficult to make and design a generic one-size-fits-all tray. Therefore some of the early trays were designed to fit onto the gums and mechanically pinch the gums in order to hold the tray onto the teeth. These mechanical trays were cumbersome and painful for patient use and became obsolete in favor of the custom tray. The custom tray involves creating an impression of the teeth, followed by casting a mold of said impression. Said mold is then covered with a pre-heated semi-molten plastic sheet with a vacuum in place in order to force the plastic to adapt to the casting's surface. Finally, the post-solidified tray is usually trimmed with scissors into a custom tray for a specific individual. The drawback to the custom tray is the amount of time and resource and effort needed to create one. The biggest drawback inherent in all trays of the prior art is their accompanying use of fluidic treatment gels and liquids. Once a tray is created it must be filled with a fluidic treatment gel or liquid and, most of the time, the patient must do this.
Early dental treatment products were liquids. Liquids were most especially difficult to handle, as they tend to run out of the trays and were easily spilled while filling the trays. Liquids were abandoned as the product of choice in favor of higher viscosity fluidic gels. Gels provide more control over flow characteristics than liquids. A gel can obtain higher viscosities that limit the flow of treatment products thereby allowing the treatment product to remain in the tray better. A gel also adds the benefit of some adhesion between the tray and teeth aiding in holding the tray in place once fitted. The drawback inherent to these fluidic gels and liquids is that they are messy for both patient and practitioner. When these fluidic gels and liquids spill while filling the tray or express out of the tray while fitting and wearing the tray; they are a nuisance and a complaint of patients. These are the drawbacks of fluidic treatment products and trays:                a. While filling trays, any spill is messy and a nuisance to clean up.        b. When fitting the filled tray onto the teeth, the teeth must displace the treatment fluids and any excess gel or liquid will be forced out of the tray and into the mouth. In the case of gels this becomes especially messy, since it cannot be easily spit or rinsed out. The current procedure calls for a toothbrush to agitate the gel and with copious amounts of dilution water, the patient will eventually work away the excess gel.        c. While wearing the trays, the upper teeth constantly come in contact with the lower teeth in a natural repetitive soft biting action. This natural biting action acts as a pump that when compressed will force more messy gel or liquid material out of the tray where it must be cleaned off or drowned in saliva. When the compression ends and the trays relax back into equilibrium it will either begin to empty out the tray and fill it with saliva (so the upper portion of the teeth are not treated) or they begin mixing and dilute the active ingredients.        
Another invention of the prior art that is used to deliver treatment gels and liquids is the dental strip. The dental strip is an insoluble flexible plastic strip onto which the treatment fluidic gels have been applied. Liquid treatment products obviously would not work well with strips, since they would just run-off the strip. The dental strip is then applied to the teeth. Current dental strips even incorporate in their design shallow pockets into the plastic strip in order to hold fluidic treatment gels. The lack of these shallow pockets would limit the amount of treatment gel available for actual treatment after fitting the strip in place, as most of the gel would be displaced from a smooth surface during fitting. The drawbacks of these prior art dental strips are again their reliance on gels for functionality. Gels suffer from many of the same problems as trays, in that while fitting and wearing the strip any excess gel that is displaced or pumped out ends up in the mouth as a constant mess. In some respects the strips are worse than the trays, since they are not tray shaped they must hold their shape against the teeth by either the adhesiveness of the gel or the rigidity of the backing material or they tend to unfold off the teeth during use. Strips that use gels also suffer from movement on the teeth during use. The gels act as a slimy lubricant between the teeth and strip, which allows the strip to annoyingly move around while it is being worn. Patients complain when they have to constantly adjust the strip back into place. One of the biggest complaints with strips that use gels is with patients with uneven teeth, the strip tends to favor the tooth that sticks out and fails to contact adjacent teeth creating a gap between the strip and teeth that allows saliva to enter, which dilutes and washes away the gel.
Other disclosed inventions include more rigid or solidified treatment compositions that are set into a tray or onto a backing material. These solidified compositions can be sufficiently rigid as to maintain itself in a tray-like configuration absent their external supports. Others disclose a strip or a tray with a two-part treatment composition that is mixed and applied to the backing material just prior to use. These 2-part prior art compositions are incapable of being combined in a pre-mixed shelf stable treatment device. When combined, the resultant compound eventually sets to a rubber-like consistency and is placed against teeth; however, this is an unstable state. Over time, the compound decomposes into a dry powder and degraded peroxide. This is why this type of prior art system must be separated into 2 parts and mixed only upon patient use. These systems require the patient or clinician to make/mix the rubber-like substance first and then somehow load this same rubber-type consistency compound onto a whitening device prior to application to the patients teeth—this is too cumbersome.
These more rigid treatment compositions are an improvement over gel or liquid compositions, since they resist flow they tend to stay on the backing strip or tray when fitting and wearing the implements. So they do not pump out of the tray or displace out of the dental strip when fitting. However, they do crack and break if flexed. The odd product is the dry or wet type patches that do not have a backing strip or tray. The drawback to patches is that they do not have a barrier between the back of the patch and the mouth; therefore they are again subject to the wiping effect of adjacent oral tissues and the washing and dilution effects of saliva. Another drawback is the lack of barrier means not only the active ingredient is treating the teeth but also treating all the oral tissues on the other side. Many of these active ingredients are irritating or harmful to soft tissue; the patch is not much of an improvement over gels and liquids that are placed in strips or trays.
The drawback to more rigid treatment compositions placed in trays or dental strips is that they are limited to non-toxic, active ingredient stable, water-soluble thickeners of the prior art. Many of these thickeners have physical characteristics so that when they are dried from an aqueous state, they are not ideal for a tray or a dental strip. The ideal thickener would have these characteristics:                a. Adhesion in aqueous environment: that when the surface of the more rigid composition becomes wetted it becomes sticky. Many thickeners do not have sufficient stickiness to overcome the forces exhibited while fitting and wearing a tray or strip to uneven teeth. The adhesion should be great enough to hold the backing strip or tray to all varieties of teeth whether straight or crooked.        b. Hygroscopic: The water-soluble thickener should be able to resist drying to a powder over long periods of storage before use. Many thickeners tend to dry out even when sealed in their packages over time leaving condensation inside the package or may even just escape the packaging altogether. A hygroscopic thickener allows you to use and keep water in the formulation during storage because hygroscopic gels will retain an aqueous equilibrium of internal water and resist drying to a powder. This amount of internal water can be adjusted as it is directly proportional to the drying temperature; therefore, drying times and temperatures can be adjusted to adjust the visco-elasticity of the final product. Thickeners that dry out are limited to formulations that contain non-volatile solvents to keep them intact. The problem with these formulations is they tend to wet more slowly reducing short-term adhesion. Many thickeners will not even create a gel without water as one of the solvents.        c. Compatible with organic solvents: The ideal thickener should be able to incorporate organic solvents to manipulate and adjust various properties. These water-soluble thickeners that can also incorporate organic solvents are adjustable in their elasticity, plasticity, solubility, tackiness and viscosity by the appropriate use of various organic solvents. A water-soluble thickener that does not incorporate organic solvents is left with only water as the modifier of choice.        d. Elasticity: The ideal thickener would have sufficient elasticity, without splitting or cracking during storage or while fitting the implement. Some devices of the prior art are of a composition that has a rigidity so as to maintain itself in the shape of its container even when the external support is removed. These compositions have essentially dried out and are solid and brittle. Many rigid compositions of the prior art are dried solids adjacent a strip or tray. The backing strip and tray are usually flexible yet the dried composition is brittle and tends to crack when manipulating the implement. There is a drawback to dry and brittle compositions in that they need lots of water to become hydrated to a point where the active ingredients become “active”. These dry compositions will tend to draw the water out of the initial wetted layer, thus drying out the surface into a less mobile layer. Also many active ingredients are volatile and would simply evaporate when dried; others are only stable in the presence of water and would inactivate the product if it were dried out. Finally a dried composition tends to lose its adhesiveness and become loose from the backing strip or tray and falls out.        
What is needed is a thickener that demonstrates all of the above characteristics that can be conjoined to a film, backing strip, backing sheet or tray in order to more efficiently deliver the active ingredients to the teeth and gums. Poly(2-ethyl-2-oxazoline) is a water soluble thickener with ideal properties attuned to the creation of pre-mixed, shelf stable compositions that may take the form of gels, visco-elastic and gelatinous compositions, that are intended to release an active ingredient. These compositions can be matched to a backing material in various designs and shapes such as a tray or dental strip.
The present invention represents a departure from the prior art in that the application of the present invention in peroxide gels allows for higher peroxide concentrations by providing a gel base that is surprisingly stable in a peroxide environment. The resultant gels may use pure hydrogen peroxide at concentrations where only adducts have been used in the prior art, thereby doubling or tripling the resultant concentration of hydrogen peroxide in the finished product while simultaneously providing comparable or superior gel stability. The present invention also presents the gels in a stable, gelatinous, visco-elastic form that is easily packaged and stored, and provides a delivery system for the same. When placed on a flexible backing, the gelatinous active component acts as a flexible adhesive that will adhere to a user's dental arch and have the thickness and elasticity to remain in place. The final product, then, is a conformable dental treatment tray that will shape itself to any particular irregularities of a user's dental arch. Therefore, it is truly customizable for the user, unlike prior art constructs.
For purposes of this Application, the term “gelatinous” shall have the definition given first in the American Heritage Dictionary of the English Language, Fourth Edition, ©2006 by Houghton Mifflin Co.: “resembling gelatin, viscous.” A gelatinous compound shall be a visco-elastic compound having physical deformation properties between a solid and a fluid. A solid shall be defined as a substance that is sufficiently rigid so that it maintains its form indefinitely, independent of any structure or support. A fluid shall be defined as a substance that will conform and coalesce to the shape of a beaker into which multiple samples of the same substance are placed, within 10 minutes, with hand agitation of the container and/or hand mixing with an implement at 25° C. with an atmospheric pressure of 1 ATM. Therefore, a gelatinous compound, as the term is used in this Application, will have some degree of flex and deformation as required to fit inside a container, but will not coalesce so that a specific sample or portions thereof are still determinable. This is particularly evident if a number of discrete units of gelatinous material are placed in a container—they will bend as they contact the container but will not merge into one body.